The process of extruding plastics to form a wide variety of articles of manufacture is well established technology. Extrusion has been is utilized to produce sheets, films, pellets, wire and cable coatings, and useful articles. Typically, a plastic material is fed to an extruder wherein the temperature is raised above the glass transition temperature of the plastic such that the plastic will flow either because it is molten or because a mechanical stress has been applied. The molten plastic is mechanically forced through a shaping or extrusion die under a positive pressure or force.
A significant drawback associated with the extrusion of sheets of different widths is the need to change the extrusion dies when it is desired to vary the width of the plastic sheet being extruded. Removing the die and replacing it with a new die of different dimensions has proved to be cumbersome and cause a significant amount of downtime on the extruders where such change in width was necessary. It has also been necessary to stockpile dies of varying widths in order to satisfy the demands of the marketplace for sheets of varying widths.
The use of an adjustable deckle or frame has been disclosed in the art to facilitate altering the width of the die and the extruded article. For example, Ryan et al. in U.S. Pat. No. 3,320,634 disclose the use of adjustable deckle plates to change the configuration of the die. Chiselko et al. in U.S. Pat. No. 3,293,689 teach the use of tracks to move deckle bars in order to regulate the width of extruded sheets. Another patent disclosing the use of adjustable deckles is Melead in U.S. Pat. No. 3,829,274.